Wet bulb thermostat control



- Oct. 29. 1940. s. M ANDERsoN WET BULB THERMOSTAT CONTROL Filed Maly 5, 1959 SHMUEL M. /INDEsoN Patented oet. 29, 1940l 2,219,661 WET BULB THERMOSTAT coNTnoL Samuel M. Anderson,

Sharon, Mass., assgnor to B. F. Sturtevant Company, Hyde Park, Boston,

MSSS.

AppueauonMey 9, 1939, serial No. 271,610

2 claims. (c1. 266-44) This invention relatesto the conditioning of air for vpassenger vehicles and has for its general object the operation of an air conditioning system for passenger vehicles to condition all outdoor air whenever feasible from an economic standpoint.

In prior air conditioning systems for passenger vehicles, such for example, as railway passenger cars, it has been the practice to supply at all -times recirculated airand 25% fresh outdoor air for conditioning air supplied to the pas- :,sngerspace. Recirculated air not only contains harmful bacteria and carries odors but its quality Cil despite all artificial conditioning cannot approxio mate lthat of temperature conditioned outdoor According to this invention, 100% outdoor air is normally used with no recirculated air admitted except at extremely low outdoor temperatures and at extremely high outdoor wet bulb temperatures.

The invention will now be described with reference to the drawing which illustrates diagrammatically one embodiment of the invention applied to a railway passenger car.

'I'he pump 5 draws water from the chilled water sump 6 through the three-way' valve 1 and pressurestat 8 and supplies it through the pipe 9 to the spray nozzles I0 in the overhead air conditioning unit II. Water returned from the spray is drained` back through the pipe I2 into the chilled water sump 6.

The blower I3 draws outdoor air through the dampers I4 and recirculatedv air through the dampers I5 and supplies it into the unit II. l, The wet bulb thermostats I6 and I1 are exposed to the outdoor air. Thermostat I1 has its contacts in the circuit including the damper motor is, the wires I9 and 2| and the emana source 20 and acts when the wet bulb temperature is at or below say F., to cause the motor I8 to adjustlthe fresh air dampers Il to full open position and to close the recirculated air dampers I5.

The thermostatIG is connected through the relay 22 to the above described damper motor control circuit and actswhen the outdoor temperature drops to 32 F.; 'o cause the motor I8 to adjust the freshV and te," culated air dampers to say 25% outdoor and/75% recirculated air.. The thermostat I1 also; akes this adjustment when the outdoor wetv 'bril .temperature is above 70- F.

The twothermostats I6 and I1 cooperate to provide outdoor airwhen' the outdoor wet bulb temperature is between 70 F. and 32F.,

preferably constructed so that the volume of wa- 'and I1 is that whichwould be evaporated therein.

-6. 1f the car temperature rises above 72 F.,

and to provide partial recirculation when the outdoor temperature is above 70 F. and below 32 F. This arrangement provides 100% outdoor air when conditions are such that too great a load on the heating or cooling systems are not required.

When the thermostat I6 acts at 32 F.\ the relay 22 is actuated to open contacts inthe circuits including the wires 23, the electric source 20, the pump motor 24, the Wires 35 and pressurestat 8, and solenoid 26, causing the motor 24 to become deenergized to stop the pump 5, and causing the solenoid 26 to open the valve 21 to drain the water from the sump 6 to prevent its freezing. 'I'he solenoid 28 is connected in shunt to the solenoid 26 and the two solenoids and themotor 24 are energized when the outdoor temperature again rises' above 32 F. by the closing of the contacts of the relay 22 and the completion of the last mentioned circuits. 'I'he solenoid 26 then closes the valve 21, the motor 24 starts the 20 pump 5 and simultaneously the solenoid 28 acts to open the valve 29 in the pipe 30 connecting the heated water source v3l and the oat valve 32` in the sump 6, to supply heated Water to the sump. 25

'I'he pressurestat 8 acts when no Water is in the pump suction line to open the energizing circuit of the motor 24 to prevent the pump from operating,

, 'I'he thermostats I6 vand I1 which may be oi' 30 any well known type are preferably provided with drip collecting funnels as illustrated and described in the application, Serial No. 231,457, iled September 24,1938 by C. W. Peterson. They are suppliedI with water through the pipes 36 and 9 from the pump 5t and when the pump is shut down, act as' dryb'ulb thermostats due to the absence of water from the evaporator sur-` faces. The internal diameter of the pipe 36 is ter suppned through it to the thermostats I6 4 I expected to be The Acar thermostat 31 has its contacts connected in thecircuit including the wires 38, 39 and 40, the solenoid 4I and the electric source 20 and acts at say 72 F. to actuate the solenoid v 4I to adjust the 3-way valve 1 so that the pump. draws water through .the bypass pipe in recir- ,l culation instead of drawing water from the sumpl 50 the thermostat'31 adjusts the solenoid 4I and valve 1 so that the pump water is drawn l,from e the chilled water sump 6. D v If the car temperature continues g' to fall after 5 the thermostat 31 has opened the bypass around the chilled water supply, the auxiliary thermostat 64 is actuated at say 68 F. to close the circuit including-the wires 45, the solenoid 66 and the electric source 2li, causing the solenoid 46 to open the valve 4'! in the pipe 48 between the steam source i9 and the air heater 5B.

It is seen that this invention not only provides an air conditioning system utilizing all outdoor air except beyond extreme temperature limits, but provides safety features preventing ,damage to equipment and avoiding discomfort to passengers.

While one embodiment of the invention has been described for the purpose of illustration, it should be understood that the invention is not limited to the exact apparatus and arrangement of apparatus illustrated since modifications thereof may be suggested by those skilled in the art Without departure from the substance of the invention.

What is claimed is: 1. An air conditioning system comprising an air conditioner, means for 'supplying outdoor and recirculated air into said conditioner, means includlng a tank exposed to outdoor air for supply-- ing water to said conditioner, means including a valve for draining the Water from said tank, and means including an outdoor thermostat for adjusting said first mentioned means for decreasing the proportion ot outdoor air and for opening said valve for draining said tank when the outdoor air approaches the water freezing temperature.

2. An air conditioning system comprising an air conditioner, means for supplying outdoor air and recirculated air into said conditioner. a wet bulb thermostat'exposed to the outdoor airentering said conditioner, means including a tank exposed to outdoor air for supplying Water to said conditioner and to said thermostat, means inciuding a valve for draining the Water from said tank, and means including said thermostat for adjusting said rst mentioned means for decreas- 'ing the proportion of outdoor air and for opening said valve. for draining said tank when the outdoor air approaches the water freezing temperature.

SAMUEL M. ANDERSON. 

